1. Field of the Invention
This invention relates to an injector to be used for supplying fuel to an engine, and more particularly to a technique to reduce operating noise of the injector.
2. Description of the Prior Art
One example of conventional injectors will be described with reference to FIG. 4 which shows a longitudinal sectional view thereof. For convenience, the left side of the injector will be referred to as the front side while the right side thereof will be referred to as the rear side. In FIG. 4, a body 101 is made from magnetic metal, for example, electromagnetic stainless. The front half portion (the left half portion) of a tubular core 102 made from magnetic material is assembled within the rear half portion (the right half portion) of the body 101. A bobbin 104 on which a solenoid coil 105 is wound in multi-layers is disposed in an annular space between the body 101 and the core 102. A connector 107 is formed by resin molding so as to cover substantially central portion of the core 102. The connector 107 is connected to a supply connector extending from an electronic controller (not shown).
Within the front end portion (the left end portion) of the body 101, a valve seat 108 having a fuel jet hole 109 is incorporated together with an adapter 110. Within the valve seat 108, a valve 112 is accommodated to be axially slidable. A C-shaped plate-like stopper 111 is interposed between the valve seat 108 and a step portion 101b of the body 101. An O-ring 119 is fitted to an annular recess in the outer periphery of the valve seat 108. The valve seat 108 is secured by caulking the front edge 101a of the body 101 to the adapter 110.
An armature 113 made from magnetic metal is fixed to the rear end (the right end) of the valve 112. The armature 113 is attracted to the core 102 when the solenoid coil 105 is energized. Inside the core 102, a pipe 114 is fixed by press fitting. A valve spring 115 is assembled between the pipe 114 and the valve 112. The valve 112 is normally biased by an elastic force of the valve spring 115 to close the fuel jet hole 109 of the valve seat 108. Thus, a fuel passage 116 is formed from a hollow space within the core 102 to the fuel jet hole 109 of the valve seat 108.
A strainer 117 is inserted into the rear end portion of the core 102 corresponding to an inlet of the fuel passage 116. The strainer 117 is formed of a net member 117a that is insert-molded into a stopper 117b. The strainer 117 is assembled by pressingly fitting the stopper 117b into the core 102. An O-ring 120 is fitted around an annular recess (not numbered) formed in the outer periphery of the core 102 near the rear end thereof. The rear end portion of the core 102 is fixedly received at a mounting port of a delivery pipe (not shown).
The operation of the above injector will be summarized below. Fuel supplied from a fuel tank (not shown) in a predetermined pressurized state flows from the delivery pipe into the rear portion of the core 102 through the fuel passage 116 into the interior of the valve seat 108. Normally, the valve 112 is maintained to close the fuel jet hole 109 of the valve seat 108 by the elastic force of the valve spring 115, so that fuel injection does not occur.
Under the above state, when the solenoid coil 105 is energized by input of an electric signal from the electronic controller, the armature 113 is retreated by the attraction force of the core 102. As a result, the fuel jet hole 109 of the valve seat 108 is opened by the valve 112, thus injecting the fuel.
When the electric signal to the solenoid coil 105 becomes off to remove the attraction force of the core 102 which has been acting on the armature 113, the valve 112 closes the fuel jet hole 109 again by the elastic force of the valve spring 115, thus resulting in stop of the fuel injection.
A conventional fuel injector other than above is disclosed, for example, in Japanese Laid-Open Patent Application No. 7-28995.
In the prior arts, operation of the above injector generates metal colliding sound when the valve 112 is retreated to abut the stopper 111 by the energization of the solenoid coil 105 and when the valve 112 is advanced to abut the valve seat 108 by stop of the energization thereof. The metal colliding sound is transmitted through the fuel passage 116 in the core 102 to the delivery pipe and emitted to the outside as a noise.